Tuning indicator in radio receivers



1948- J. c. STANNOW TUNING INDICATOR IN RADIO RECEIVERS Filed May 23, 1945' v INVENTOR. JRGEN CHRlSTlAN STANNOW ATTORNY Patented Dec. 21, 1948 TUNING-INDICATOR IN RADIO: RECEIVERS;

Ji'irgn christian stannow, tiaingo;, sweden,,as s'ignor, by mes'ne assignments; tWHtiz'ltiiie re search; I'm, ohicage 111., aorporatiencf Illinoi's Applicationglyiay .23,;1945,.Serial.l\l 595,291. In Sweden June.14,,1944

Claims: 1 My'mvention relates to a tuning indicator in radio receivers.

My present invention relates to anew form of' voltage indicator having utility in'numerous and diverse applications. Among such uses, however; the invention is particularly applicable to tuning indicators in radio receivers and inithe" following it will therefore be described in connection with such an application.

One form of tuning indicator hitherto commo'nly' us'e'd" iii radioreceivers utilizes asmall cathode ray tube constructed inaco'irinion enve lope with anamplifier tube. The tube is so formed and is connected to the apparatus in such a way that one or more luminous surfaces usually'in the shape of circular sectors orcircular riiigs" appear on its fluorescent screen, the centre angle of the circular" sectorsor the'width of the circular rings being a measure of the mag"- nitride of the applied voltage;

Tuning indicators of the cathode ray tube type, however, are relatively complicated and expensive and furthermore they consume power for the heating of their cathodes. These drawbacks are avoided in another form of tuning indicator which uses a glow discharge tube having a long straight cathode, an igniting electrode and a control electrode. If to the igniting electrode of such a tube there is applied a suitable voltage capable of firing the tube and maintaining a feeble discharge, the extension of the glow light along the cathode within a certain range will be dependent upon the voltage applied to the control electrode. As is well known, this phenomenon is due to the property of the glow discharge to adjust itself automatically to optimal current density at the cathode surface. However, the range of control voltage over which such a glow discharge tube may be controlled is relatively narrow for a tube with reasonable dimensions and it can be increased only by making the tube unduly long.

The present invention refers to a tuning indicator of the glow discharge tube type in which the above-mentioned drawback has been removed and furthermore the tube has been given such a form that it does not require more space than an indicator tube of the cathode ray type and thus from a spatial point of view can replace such a tube.

In accordance with one form of the invention, a cathode-glow-discharge type of incrementalvoltage indicator comprises a gas-enclosing envelope, a cathode of conical spiral configuration supported within the envelope and having a pitch between its" turns comparable to: the diam ter or supported to extend" within the envelope only at the region of. the apex of the embeds and at a distance therefrom not substantially greater thevalue of the aforesaid'turnspitch.

The invention will now be more fullydescribedwith; reference to the accompani'y'ihg which shows a glow discharge tube according w corii'call spiral with its apex towards the'' glass" stem; andtwo sma1l-ignitingand control electrodes rand-5. The cathode'i's' mad-ear iron or other convenient material and is activated in a suitablemanrier.

Iii usin the glow discharge tube as" awnin indicator in a radioreceiver, the cathode; is prerg erabl'y connected to'gro urid" potential. Theorie of" tl'ieelectrode's 4'" and 5 wmenismteneedw function as an igniting electrode is connected to a source of positive voltage, having a value of potential higher than the igniting voltage of the tube, through a high resistance which is dimensioned in such a manner that a very feeble discharge is maintained after the tube has ignited. To the other one of the electrodes 4 and 5 which is intended to serve as a control electrode there is supplied, possibly through a series resistance or from a voltage divider coupling, a varying direct current voltage which in a known manner is obtained from the screen grid voltage or anode voltage of the amplifier tubes and which varies in accordance with the strength of the amplified signal. For control voltages higher than the voltage on the igniting electrode when the tube is firing, the extension of the glow light along the cathode in a direction away from the glass stem will vary proportionally to the difierence between the voltages on the control electrode and the igniting electrode.

The glow discharge tube is preferably mounted on the control panel or the tuning dial of the radio receiver so that it can be viewed from its top. To an observer the glow light will then appear as a circular luminous surface whose magnitude varies with the applied voltage. In the application as a tuning indicator, the tuning of the receiver is therefore varied, until the glow light attains its greatest extension, at which time the receiver is correctly tuned to the desired signal.

Due to its spiral form, the cathode can be made of appreciable length without the dimensions of the tube acquiring ungainly values. This has the advantage that the control-voltage range can be made relatively Wide. As compared with tuning indicators of the cathode ray type, the glow discharge indicator. possesses the advantage that it does not consume any heating power so that it can be used in battery receivers without increasing the load on their batteries.

Although the invention has been described above with reference to one embodiment only, it will be evident that several changes and modifications may be made Without departing from the inventive idea. Nor will the range of application of the invention be considered limited to tuning indicators in radio receivers, but it may also come into use as a voltage indicator in a plurality of apparatuses of other types, e; g. in measuring bridges and similar devices. 7

What is claimed: 3

.1. A cathode-glow-discharge type of incremental-voltage indicator comprising, a as-enclosing envelope, a cathode of conical spiral configuration supported within said envelope and having.

a pitch between its turns comparable to the diameter of the mean turn thereof, and a control electrode supported to extend within said envelope only at the region of the apex of said cathode and at a distance therefrom not substantially greater than the value of said pitch.

2. A cathode-glow-discharge type of incremental-.voltage indicator comprising, a gas-enclosing.

envelope, a cathode of conical spiral configuration-supported within said envelope and havingv a pitch between its turns comparable to the diameter of the mean turn thereof, and exciting and control electrodes supported to extend within said envelope at the region of the apex of said cathode and at a distance therefrom not substantially greater than the valueof said pitch.

3. A cathode-glow-discharge type of incremental-voltage indicator comprising, a gas-enclosing I tion supported within said envelope, said envelope having at least a transparent window portion of an area comparable to the projected area of the large end of said cathode and coaxially aligned with said cathode at the region of said large end thereof, and a control electrode supported to extend within said envelope only at the region of the apex of said cathode.

5. A cathode-glow-discharge type of incremental voltage indicator comprising, a gas-enclosing envelope, a cathode of conical spiral configuration supported at its apex within said envelope,

and exciting and control electrodes supported by v said envelope to extend therewithin at the region of the apex of said cathode and relatively closely spaced thereto.

JdRGEN CHRISTIAN STANNOW.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,595,735 Schmierer Aug. 10, 1926 1,815,762 Charlton July 21, 1931 1,860,035 Kowvallis May 24, 1932 1,961,575 Senauke June 5, 1934 1,961,748 EWest June 5, 1934 1,984,469 Ewest Dec. 18, 1934 

